A084194 Even numbers n such that the sum of the digits is prime and the sum of the digits of n/2 is also prime.
14, 32, 50, 58, 76, 94, 98, 104, 122, 140, 148, 166, 184, 188, 212, 230, 238, 256, 274, 278, 292, 296, 302, 320, 328, 346, 364, 368, 382, 386, 410, 418, 436, 454, 458, 472, 476, 490, 494, 500, 508, 526, 544, 548, 562, 566, 580, 584
Offset: 1
Examples
3+2=5 for n=32 and 1+6=7 for n/2=16; 5+8=13 for n=58 and 2+9=11 for n/2=29; 2+1+2=5 for n=212 and 1+0+6=7 for n/2=106; 2+5+6=13 for n=256 and 1+2+8=11 for n/2=128.
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Crossrefs
Cf. A084201.
Programs
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Maple
filter:= proc(n) isprime(convert(convert(n,base,10),`+`)) and isprime(convert(convert(n/2,base,10),`+`)) end proc: select(filter, [seq(i,i=2..1000,2)]); # Robert Israel, Sep 04 2019
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PARI
isok(n) = {if (n % 2, return (0)); dn = digits(n); dh = digits(n/2); isprime(sum(i=1, #dn, dn[i])) && isprime(sum(i=1, #dh, dh[i]));} \\ Michel Marcus, Aug 12 2013
Extensions
More terms from Michel Marcus, Aug 12 2013
Comments